Nasal masks are commonly used in the treatment of respiratory conditions and sleep disorders (e.g., obstructive sleep apnea) by delivering a flow of breathable gas for, or to assist patient respiration. These nasal masks typically receive a gas supply line which delivers gas into a chamber formed by walls of the mask and the user's face. The walls usually are semi-rigid and have a face contacting portion including an aperture which is aligned with the wearer's nostrils. The face contacting portion can comprise a soft, resilient elastometric material which may conform to varius facial contours. The mask normally is secured to the wearer's head by straps. The straps are adjusted to pull the mask against the face with sufficient force to achieve a gas tight seal between the mask and the wearer's face but not so tight as to be uncomfortable. Gas is thus delivered to the mask and into the wearer's nasal passages.
Problems often arise with masks of the above configuration. For example, the mask may be dislodged, thereby breaking the seal between the mask and wearer. This may occur if the wearer rolls over when sleeping thereby creating a drag force on the gas supply line which is transmitted to the mask, breaking the seal. In the case of a mask being used for the administration of Continuous Positive Airway Pressure (CPAP) treatment for the condition obstructive sleep apnea, such a leak can result in the pressure supplied to the entrance of the wearer's airway being below the therapeutic value, and the treatment becoming ineffective.
Another problem is the face contacting portion may apply excessive pressure to the wearer's face resulting in discomfort and possibly skin irritation. This can occur because the face contacting portion has to distort beyond its normal range of elasticity to conform to certain facial contours which requires the application of excessive forces. In some cases these excessive pressures and forces may cause the face to distort to conform with the face contacting portion to increase wearer discomfort, resulting in facial soreness and ulceration.
An example of the respiratory mask useful in the CPAP treatment is in U.S. Pat. No. 6,112,746 issued to Kwok et al. Sep. 5, 2000, the entire disclosure of which is incorporated by reference. That patent lists over 200 pieces of prior art generally pertinent to the subject invention. The present invention relates to a cushion for a respiratory mask which is more comfortable and provides a superior seal than heretofore available.
These and other advantages will be described in more detail below.